1. Field of the Invention
The present invention relates to a wettability variable substrate provided with a wettability variable layer constituted of a co-hydrolysis condensation polymer of an organosiloxane precursor, for example, a fluoroalkylsilane compound and an amorphous silica precursor, and to a functional element formed using the wettability variable substrate by utilizing a difference in wettability which is caused by exposure under the presence of a photocatalyst. Also, the present invention relates to a wettability variable layer forming composition used for forming such as wettability variable layer.
2. Description of the Related Art
As a method of forming a fine pattern, there is a method in which a photoresist layer provided on a raw material which can be etched is subjected to pattern exposure and developing, and etching is carried out utilizing the resultant resist pattern; or a method in which a functional raw material for imparting a necessary function is dissolved or dispersed in a light sensitive resin composition, a layer of the light sensitive resin composition is laminated on a substrate, and pattern exposure and developing are carried out in the same manner as above to pattern the layer of the light sensitive resin composition.
In both of these methods, since developing or etching is carried out, the necessity for treating an effluent, containing the removed resist and raw materials which can be etched, arises and also there is the problem that when functional raw materials are contained, the raw material is deteriorated by an alkali solution and the like used for developing. Also, a printing method can be utilized as a method of producing a fine pattern. It is however difficult to form a highly precise pattern because of a restriction on precision.
As disclosed previously in Japanese Patent Laid Open (JP-A) No. 2000-249821, the inventors of the present invention have proposed to adhere a fine pattern additionally by utilizing a pattern based on a difference in wettability which is obtained by varying the wettability of the surface of silicone and the like by using a photocatalyst. And the inventors found that by using a polysiloxane containing a fluoroalkyl group particularly as the raw material causing the variation in wettability, the drawbacks of conventional methods using a photoresist or a light sensitive resin composition are solved.
Generally, in order to form a polysiloxane containing a fluoroalkyl group on a substrate, an acid or alkali catalyst is added in a coating solution of a fluoroalkylsilane compound which is a precursor of a fluoroalkylsilane to promote hydrolysis and a condensation polymerization reaction, thereby reacting with the surface of the substrate. There is a problem that if these catalysts are added to the coating solution, usable time of the coating solution is shortened or an excess fluorine type component remains on the surface of a wettability variable layer. Because of this, the wettability variable layer becomes clouded and it is necessary to add a wiping process. If no catalyst is added in order to avoid the cloud, the reactivity with the surface of a substrate drops and therefore, a layer having the characteristics such as sufficient durability (adhesiveness), transparency or liquid repellency is not obtained as the resulting wettability variable layer.